Maybe because playing a game is not one of supposedly devil work description ???
(Just a joke...)
Press the NUM LOCK Button in your key board, sometimes it enabled u to activated all of your FUNCTION BUTTON in your keyboard so the system can recognized that you have press F1 button then...
Also, free trainer usually available only for early version or original version so if u had update or patched your game, u need to reinstall the game in original version too